Uplifting celebrations to suppress time in POW camp (6)
I believe the answer is:
stalag
'pow camp' is the definition.
(I've seen this before)
'uplifting celebrations to suppress time' is the wordplay.
'uplifting' says the letters should be written backwards.
'celebrations' becomes 'galas' (gala is a kind of celebration).
'to suppress' indicates putting letters inside (inserted letters are suppressed or crushed).
'time' becomes 't' (abbreviation).
'galas' enclosing 't' is 'galats'.
'galats' back-to-front is 'STALAG'.
'in' is the link.
(Other definitions for stalag that I've seen before include "German World War two prison camp" , "German camp for POWs" , "German POW camp in WWII" , "Type of German prison camp" , "Water at the mouth" .)